A combination treatment using ethyl formate and phosphine to control Planococcus citri (Hemiptera: Pseudococcidae) on pineapples

Citrus mealybug, Planococcus citri (Risso), is a known quarantine pest that is difficult to control with phosphine (PH3) or low concentrations of ethyl formate (EF), particularly at low temperatures. Methyl bromide (MB) is a fumigant used for quarantine and preshipment (QPS) that can eradicate target pests with short fumigation periods. However, MB, which is an ozone-depleting substance, is scheduled to be phased out in South Korea over the next decade. There is no ideal alternative fumigant to replace MB for QPS of perishable commodities. A laboratory study was conducted to compare the individual effects of EF and PH3 individually, and the effects of EF mixed with PH3 as an MB alternative for the control of P. citri adults, nymphs, and eggs. In comparison to treatments with EF and PH3 individually, EF mixed with PH3 resulted in high toxicity to all stages of P. citri. The eggs were more tolerant than the nymphs and adults. A mixed treatment of EF and PH3 achieved complete control of eggs infesting pineapples at concentrations of 25.1/1.0 (EF/PH3) mg/liter at 8 degrees C for 4 h of exposures. This new combined EF/PH3 fumigation technology could offer shorter exposure times and less damage to perishable commodities at low temperatures, and could potentially be extended to controlling other quarantine pests as a replacement treatment for fruit and vegetables in which methyl bromide is currently being used

Chemically-specific time-resolved surface photovoltage spectroscopy: Carrier dynamics at the interface of quantum dots attached to a metal oxide

We describe a new experimental pump-probe methodology where a 2D delay-line detector enables fast (ns) monitoring of a narrow XPS spectrum in combination with a continuous pump laser. This has been developed at the TEMPO beamline at Synchrotron SOLEIL to enable the study of systems with intrinsically slow electron dynamics, and to complement faster measurements that use a fs laser as the pump. We demonstrate its use in a time-resolved study of the surface photovoltage of the m -plane ZnO (View the MathML source101¯0) surface which shows persistent photoconductivity, requiring monitoring periods on ms timescales and longer. We make measurements from this surface in the presence and absence of chemically-linked quantum dots (QDs), using type I PbS and type II CdSe/ZnSe (core/shell) QDs as examples. We monitor signals from both the ZnO substrate and the bound QDs during photoexcitation, yielding evidence for charge injection from the QDs into the ZnO. The chemical specificity of the technique allows us to observe differences in the extent to which the QD systems are influenced by the field of the surface depletion layer at the ZnO surface, which we attribute to differences in the band structure at the interface